Coking of carbonaceous fuels



Aug. 26, 1952 w. A. REX 2,608,526

COKING OF CARBONACEOUS FUELS Filed Dec. 14, 1946 l at'ented Aug. 2 6 i952 COKING OF CARBONACEOUS FUELS Walter A. Rex, Westfield, N. J assignor to Stand ard Oil Development Company, a corporation of Delaware Application December 14, 1946, Serial No. 716,409

16 Claims. ((21. 1961-5 The present invention relates to the carbonization or coking of carbonaceousfuels such as heavy oil residues, asphalts, asphaltites or the like, as well as all types o f coal, lignites, cellulosic materials including lignin, oil shale, tar

sands, etc., to produce valuable volatile mate rials andcoke. More particularly, the invention is concerned with an improved method and apparatus for the continuous carbonization of these fuels in the'form of finely divided solids moving much like a fluid through a treating'system.

Heretofore, carbonizable fuels of the type mentioned above have been converted into liquid and gaseous fuels and'coke in fixed bed, low or high temperature, coking 0r carbonization processes. 7

These processes either require frequent cleaning periods resulting in discontinuous operation or they involve inefficient conversion of the available carbon into heat and volatile fuels.

The operation oft hese processes may be made fully continuous by employing the so-called fluid solids technique in which the reactions take place indense fluidized .beds of finely divided solids maintained. in -a turbulent ebullient state by means of fluidizing gases, This technique has highly desirable additional advantages including greatlyimprovcd heat distribution and ease of solids handling] 7 It is also known that the utilization of the carbon available in the starting material may be greatly intensified when the coking is carried out in a so-called fluid" reactor and the heat required to support the endothermic coking reaction is generated by a combustion of the carbon of the charge and supplied to the coking zone for instance in the form of sensible heat of solid combustion residue circulated to the heat-consuming-,vcarbonization or coking reaction. In this manner, it is also possible to supply the heat required for the coking reaction directly and internally to the charge-undergoing coking with-.

ol l' ranundesirable. dilution of the volatile carbonization products with combustion gases and without losses of valuable volatilecarbonization pro ducts-by combustion.

However, even this improved coking or carboni zation process falls short of a full utilization oi the valuableflconstituents of the charge in commercial operation. In order, to carry the coking procedure to substantial completeness,

coking times are usuallyrequired which are conducive tothe' craking of valuable normally liquid coking products into gases of lower. value. In addition, continuous coking processes applying the fluid solids-technique involve the use of dense solids technique.

highly turbulent coking beds ofsubstantiallyuni l form composition throughout the bed to which the charge is continuously fed. and from'which,

coke is continuously withdrawn. The coke withdrawn will, therefore, always have an average].

composition between that of the fresh feedl'and that of a completely coked or carbonized product rather than the composition of a completely coked product as it would be desirable from the point of view of process economy as well as value;

of the coke product for various uses. 1 The present invention overcomes the afore mentioned difficulties and affords various addi: tional advantages as will appear from thefollowing description thereof read with reference to the accompanyingdrawingr It is, therefore, the principal object of my in vention to provide an improved process forthe continuous coking or carbonization of carbonaceous fuels. l l

Another object of my invention is to provide an improved coking or carbonization process, which combines continuous operation with shortreaction times and the production of a. sufficiently;

coked residue. A still further objectof my invention is to provide an improved coking or carbonization proo ess of the type specified which employs the fluid A more specific object of my improved process of coking heavy oil residues;

asphaltites, carbonaceous solids etc. in ;contin-i-i of valuable? uous operation'with optimum yields volatileproducts.

Other and further objects and advantages of my invention will appear from the following more detailed description and claims. 7?

I have found that these objectsand advan of the feed but insu fficient to permit appreciable cracking of volatile products. Carbonaceous charge and heat-carrying solids ar preferably. passed upwardlythrough the transfer line coke ing zone. A fiuidizing gas injected into a bottom portion of the transfer line serves, in .lco'mbina fl tion with product vapors, to fluidize and propel the charge through the coking zone.

Finely divided fluidized coke and invention is an vapors discharge into a disengaging and/or stripping zone of enlarged cross section which is maintained below cracking temperature and wherein coke is separated from and/or stripped of, volatile coking products preferably with the aid of a stripping gas such as steam, CO2, other inert gases, or the like. Finely divided coke, substantially free of product vapors is preferably heated by a partial combustion in a separate heating zone to the desired solids preheating temperature and returned as heat-carrying solid to the transfer line coking zone.

An elongated transfer line of relatively narrow cross section may be readily so dimensioned as to restrict the reaction time to that required for substantially complete coking at the coking temperature employed without permittingappreciable cracking. At the same time, solids backmixing is limited to a negligible extent while full advantage may betaken of the ideal heat distribution within the fluidized mass across the (0.85 section of the narrow coking zone. In this manner, a coke of any desired low volatile content may be withdrawn from the discharge end of;the transfer line reactor.

My invention isequally suited to the coking of carbonaceous materials which are liquid at theicoking temperature such as heavy oil residues, asphalts, gilsonites'or the like, as to the carbonization of carbonaceous solids such as coals, oil shale, etc. In the former case I inject the preheated liquid charge into a fluidized mass of; hot coke or inert solids such as sand, clay, etc. maintained in my transfer line reactor. In the lattercase,- the finely divided solid charge is fed to the transfer line reactor'and contacted therein with-fluidized hot usually carbonaceous solid obtained'in' the'process. In both casesycomplete mixing takes place immediately upon contact of the fresh charge with the hot fluidized-solids mthe transfer line reactor. However, greatest advantagesare obtained when applying my invention to the -coking of less refractory charge materialssuch as oilresidues, asphaltitesand the like which have been found to yield -volatile coking products of particularly high cracking sensitivity. 7 i

-Inorder to assure full continuity ofoperation, I prefer to maintain the process solids in a fluidized': condition in all stages of the process including the reaction... disengaging and combustion-zones. :Any conventional meansknownin the=ar't:-of- :fluid: solids handling suchas aerated standpipes, pressurized feed hoppers, mechanical conveyors-etc. may be used to convey the process solids between the individual treating zones.

Specific equipment dimensions and operating conditions. depend, of course, on the characteristics of1the carbonaceous: feed and the quality andrelative proportions of the products desired.

Quite-generally,.satisfactory results may be ob-' tainedwhen using a transfer line reactor allowing feta; feedresidence'time of about 0.5 to 15 seconds 1 at coking temperatures of about 850--1400 E, pressures of about 1-50 lbs. per sq. in..,and;;superficial gas velocities of about'2-30 ft.- pcr second; for solids particle sizes of about 5,0-200-meshwand bed densities of about 0.1-10 lbs per cu. ft. within the transfer line reactor. Coke disengagingand/or stripping may be carried out atv a temperature level of about 700- '1300F. and 25 lbs. persq. in. pressure. The heat-carrying solids are preferably preheated to'temperatures of about 10001 800 F. assuming a feed ratio of about 1 to lbs. of heat-carrying solids supplied at the preheating temperature my invention.

The system illustrated by the drawing essentiallycomprises a transfer line reactor ID, a combination disengaging and stripping vessel 20 and a combustion zone or heater 50 whose functions and cooperation will be forthwith explained using the coking of heavy oil residues as. an-example. 1 It should be understood, however, that the system illustrated may be readily adapted to the coking or carbonization of other carbonizable fuels such as asphalts, shales, coals, etc.

Referringnow in detail to the drawing, heavy oil residues'such as a l7 A.-P. I. East Texas residuum isfed through line l---to apreheating furnace 3 in which the feed' may be preheated to a temperature of, say, about500--850- F. at which no appreciable coking takes 1 place. The 7 preheated feed leaves preheater 3 through-lined and is injected into the lower portion of transfer line reactor [0 with the aid of a propelling and fiuidizing gas such as steam; COa-product gas, or the like, supplied from-line 5.

Transfer line reactor ll] receives; froma conventional standpipe 12 provided with control valve [4 andoneor-more aeration taps l6; finely divided process coke having a fluidizable particle size-of about 50-200 mesh, which has beenheated to a temperature of about 1000-1600'F. in heater 50 as will appear more clearly hereinafter. "*In the case of'a coking feed which isliquidat' the coking temperature, the coke particles-supplied fromstandpipe l2 consist of process cokedeposited on a core of non-process solid such as extraneous coke, sand, clay or the like supplied to and heated in heater 50 above coking temperature during the starting period inany suit able manner known perse. .Eorexample; the extraneous finely divided solids may,-during the starting period, be suspended in an air-fuel gas mixture and the suspension may be passed through line 45 intoheaterillwherein-the gas mixture may be burned toheat the solids to the desired temperatures. In the course of the operation all extraneous solid matter may di's-' appear in 'theformofwithdrawn cokeand-be' replaced completely by process coke.

The liquid feed, upon contact withthe-hotobke in reactor I0, is quiokly'heated tda coking-or carbonization. temperature of about 850-1200"--'F. as a result'of' the excellent heat transfer characteristics of the turbulent coke mass fluidized in and propelled through reactor 10' under the influence of the fluidizing gas supplied through line Band the rapid evolution of product vapors. Coke formed during the coking treatment-is deposited on the fluidized solids in reactor 10. The diameter and slope of reactor), and the feed rates of the. charge, preheated solids and fluid- 'izing gas are'so chosen that the solids in reactor [0 form-an ebullientfluidized massand travel upwardly through reactor [0. Thelength erreactor I0 is adapted to permit acokingtime ofabout 1 to lfl'seconds so that the charge of:reactor I0 discharges into vessel-illsubstantially at.- the coking temperature which -;may equal .or: be even above the temperature of incipient cracking ofvolatlle: coklngproducts after the coking of thecharge is carried to substantial completion yielding a coke substantially free of carbonizableconstituents.

' In order to prevent substantial. cracking of volatile coking products, it is desirable to quench the entry of the suspension into the enlargedsection 22 of vessel 20. I may also quench the coked suspensionprior to its entry into vessel by introducing into an upper portion of reactor l0, e. g. through line 11 suitable amounts of a preferably liquidquenching medium such as water, liquid feed, heavy recycle slurry of solid. coke in heavy product bottoms from the product recovery system. etcpor by any combination of these methods. If water or any other extraneous quenching liquid is used in this manner, it may be desirable to allow for a contact time between the coked suspension and the quenching liquid suflicient to permit vaporizationof the latter.

For the specific charge here referred to, based on a feed rate of about 50-150 bbl. per hr., reactor I0 may have a diameter of 16 to 40 in., a length of to 90 it. and a slope of 20 to 90. Assuming a feed preheating temperature or about 850 and an initial temperature of the heatcarrying solids of about 1200 F., good results -may be obtained at superficial gas velocities within ree actor. ll] of about 10 to ft. per second and a solids feed rate through valve l4 of about 3 to 6 lbs. per lb. of fresh charge.

A relatively dilute suspension of finely divided product coke in fluidizing gas and product vapors discharges into the upper enlarged section 22 of vessel 20, which may attain a temperature or about 800-ll00- F. As a result of the. reduction of the superficial gas velocity, a substantial proportion of the suspended coke drops out and is collected in the lower section 24 which may be provided with baflles .126. A small amount of a stripping gas, preferably steam, such as about 15% of steam by weight of carbonaceous charge, is injected into the bottom portion of section 24 through lines 28 to strip the coke collected in section 24 of associated product vapors and simultaneously to keep the coke in a fluidized state.

A mixture of product vapors and fluidiaing gas containing some entrained coke is withdrawn overhead'from" disengaging zone 22 and passed through conventional gas-solids separation equipment such as cyclone 30. in cyclone 30 may be circulated through 1ine.32

to the coke bed in stripping section 24. Product vapors and gases, now substantially free of coke, are withdrawn through line 34 to be .passed to any-conventional product recovery system (not shown) a i l In accordance with another modificationof my invention, substantial cracking of volatile coking products may be prevented by introducing the coked suspension from reactor [0 through line 19 directly into cyclone 3|] In this manner, the product vapors are separated immediately from the hot coke and withdrawn from hot surfaces without time being allowed for any appreciable cracking.

Stripped fluidized product coke, which is practically free of carbonizable constituents, is with- Coke' separated through a conventional standpipej provided aerating;r

with control; valve 38 and one or more taps 40.

Fluidized supporting gas such as air. and/or oxygen fed from line 43. The dilute suspension formedis passed under the pseudo-hydrostatic pressure of ebullient bed fluidized by the combustion-supporting gas and the gaseous combustion products.

Combustion of coke in heater 50 takes place at temperatures which may vary between 1000 and 1600" F. depending on the oxygen supply which may be readily adjusted to the heat requirements in reactor to. Superficial gas velocities of about 0.5-1.5 ft. per second in heater 50 and an oxygen supply of about 0.07 to 0.20 lb. per lb. of heavy residue charged are generally suitable for this purpose. Flue gas is taken overhead from level L50 of the fluidized heater bed and preferably passed through conventional gas-solids separation equipment such as cyclone 52.. 'Separated coke lines may be returned through pipe 54 to the fluidized heater bed while hot flue gases substantially free of solids are withdrawn through line 56 to be putto any desired use ,or

to be vented, preferably after a suitable heat exchange with process fluids and/or solids;

l luidized residual coke is withdrawn downwardly from heater 5!? and passed substantially at the heater temperature through standpipe [2 l with process fluids or solids, or from stripping section 24 through line 29.

As mentioned above, the system illustrated by. the drawing may also be used for the carbo'niz'a-f; tion of carbonaceous materials which are solid-at the carbonization conditions such as all types or coals, oil shale, cellulosic materials, and t'he like. When such materials are used they may be sup plied in a fluidizable particle size from a feed hopper 10 through a conventional standpipe 12 aerated through one or more taps 14 and provided with a control valve 16. The fiuidizedsolids feed discharges into line wherein it may be suspended in a propelling or fluidizing gas 'such" assteam and supplied to reactor l0 tobe fur-' ther treated substantially as described above.

The turbulent state of the solids charge-of reactor lll affords immediate and complete' mixing and heat exchange-with the hot solid suppliedfrom standpipel2. i

It Will be understood that standpipes 12. 3t and 12 should be high enough to exert sufficient-1137 drostatic pressure on their bases to overcome the pressure and frictional resistance in the direc tion of the contemplated flow of thesclidsfrom these standpipes through the system. Othercon ventional means for conveying fluidized solids such as pressurizedfeed hoppers, mechanical conveyors or the like may replaceany or ,all 'oi'. standpipes I2, 36 and 72. Instead of suspending the solids withdrawn from stripping zonel24 a air line 45 these solids may be fed directlyfa'nd drawn, downwardly ,from stri ing zon n n e tly P lh a ly ta .llels tq; 1

coke from standpipe 36 feeds into. line 45 wherein it is suspended in a combustionstas s-sc an conventional manner. "If desired; a-' com 1 within reactor l0. Other-modificationsofthe system illustrated may appear to those skilled in the art without deviating from the spi'rit and scope ofmy invention.

'My invention will be further illustrated by the following-specific example.

' Example FeedlZThA? P. LlEast Texas-residuum:

. Feed preheat in furnace 3 l. 850 F.

Feed rate thin-4. .Average temperature in reoeto Average pressure in reactor 10. Average temperature'in vesselSO .Averagepressure in vessel'50 2 p. s. i. g. Length reactor-l0 60 Slope reactor 10 v.Diameter reactor-10..., Average temperature vessel 22 'Averagepressure vessel 22 s. i. g. ..Average particle size circulated coke; 40-200 microns.

Cokernte thru valve 14 3.4# coke/#ieed. Air rate thru line'43 i l 4 6 S. C. F: air/# feed 'Colce rate thruvolve fls A a 3.5#'coke/# feed. Stripping. steam thru'line 28 1 weight percent on feed.

Diameter stripping section 24 e eeeee 24 in.

.QDiorneter disengaging-section 22 ft. 9 in.

Liquid'quench Water temperature 65 F.

7 Liquid quench water rate thru' 77 weight percent on feed.

3 Steam injection thru line' 5 3-weight percent on feed.

Short Oonven Cont-a ct tionol Fluid Time Technique Comparison for yields;

Coking temperature, F. 990 990 P rcssure, p. s, i. g 15 15 'Feeil rate volume liquid.

Feed/volume reactor/hr... 3.8 0. 30 Contact time, secondsm 3 15-25 Yields:

.ZDry gas, weight percent. n. 10.7 15: 0 Total distillate, volumepercent 82. 3 76.0 Coke; weight percent 9. 3 12. 0

withinthe scope .of the invention. Only such limitations should be imposed on'the invention asare indicated in the appended claims.

I claim:

1. Theprocess of producing volatile fuels from carbonizable materials at'a carbonization temperature which comprises passing carbonizable material through an elongated narrow path' in contact with a mass of finely divided solids fluidized byan upwardly flowing gas and'heatedv independently of said carboniza-ble material at least to said carbonization temperature, for a time of about0l5-l5 seconds sufficient to carbonize said carbonizable .ma'terial substantially completely but'insuflic'ient to. permit substantialcrackin of volatile carbonization products to gases, controlling the flow velocity'of said gas between-about 2-30 'ftgper second so as tomaintain high turbulence ofsaid mass across the cross-sectional area of-"said' path and to force said gas an'dsaid mass. in the same direction upwardly through said path-while preventingsubstantial' bacl miiiiiig oi solids5 against the 'flow direction of th'e' chatg discharging" fluidized solids arid volatile products into a disengaging zone, WithdraWing 'finely -divided coke'from said disengaging zone and withdrawing volatile carboniz'ation products from-said disengaging zone. 1 a Y 2. The proces of-claim 1 wherein -said earbonizable material is; liquid at s'aidcarbonizati'oni temperature. a

3. The process of" claim I 1 wherein said 'ca'rbonizable material is solid at the carbonization temperature.

mass of solids comprisesproduct coke. 5FTheprocess of produfi-hg volatile products from carbonizable fu'els- -by; subjectingl saidi fuels to= a carbonization temperaturewhich comprises: passing carbonizable 'materi-al 'upwardlythrough an elongated narrow ath incontact witnatun bulent mass of finely divided solids fluidized by an upwardly fiow'ing gas -an'd heate.d independ.-.

ently of said carbonizable-material at.-least t0 saidca'rhonizationtemperature, forlattiine :of about 05-15 seconds sufiicient to -carbonizeisaid carbonization products to; gases-controlling the:

flow velocity of: said-gas betweeni-about.: 2-30:' ft.

per second so as-to maintain high turbulence of.

said mass across the cross-seetionaliarea. ot said path and to forcesaid:v gas andl'said massr in the same direction upwardly throughi said path while preventing substantial "back'emi'xing of"'so1ids' against the flow directionT-oithe charge, discharging fluidized solids 'and"volatileiproductsfrom said path into a -disengaging zone, withdrawing volatile A carboniza'tion."products from said -zo'ne, separately withdrawing" finely divided coke from. saidzone, passing finely. divided. coke. thus withdrawn -to"a combustion zone, subjecting finely divided cokein said combustionzone:toe-"combustionlreaction to heat said coke at :least to a saidcarbonizatioir temperature and passin'gfinely divided cokelso heated. from" sai'dicombustion' zone to said path at..airateisumcientxtozsupply at least.

a portion ofithe'heat of .carbonizationi required on said path.

. 6. The' processiof cl'aim *5: wherein said coke is stripped of associated volatilecarbonization prod? ucts prior to passing said coke to said combustion zone.

7. The process of claim :5iwhereinsaid-coke:is subjected to said combustion reaction in a dense turbulent bed of finely divided'solids fluidized by an upwardly flowing combustion-supporting. gas.

8. The process of claim 5 wherein the temper ature in saiddisengagingzone is below the incipient cracking temperature of volatile carboniza- 'tion products;

'9. Theprocessof claim 5 wherein said carbonizable material is liquid at said carbonization temperature and said fluidized massoomprises a finely divided extraneous solid.

10. The process of claim 5 wherein the -temperature in said disengaging zone is substantially the same-as said carbonization temperature.

11. Theprocess of claim 5 wherein said-solids and-volatile-products in said path are quenched to a temperature below incipient cracking temperature prior to the separation of cokelfrom volatile products.

12. In the process of continuously carboni'zing carbonizable fuels in the fornrof a turbulentbed of fluidized solids maintained in'a carbonization' 9 zone and supplying heat of carbonization as sensible heat of finely divided product coke heated by a combustion reaction carried out in a dense fluidized bed of product coke maintained in a separate combustion zone, the improvement which comprises controlling the carbonization time at a length within about -15 seconds desirable for the prevention of cracking of volatile products to gases by passing said carbonizable material in contact with a fluidized mass of said heated coke at a controlled rate upwardly through a carbonization zone forming an inclined elongated narrow path having a ratio of length over diameter of at least 7 and a diameter adapted to permit at the prevailing flow rate turbulence of the charge across the cross-section of said path and to prevent substantial backmiXing of solids against the flow direction of the charge.

13. The process of claim 12 wherein fluidized coke and carbonization products flow in the same direction upwardly through said path.

14. The process of producing volatile products from liquid carbonizable fuels of comparatively high specific gravity and high viscosity yielding volatile coking products of high cracking sensitivity, which comprises subjecting said fuels to a carbonization temperature within the range of 850 to 1200 F., passing said carbonizable fuels upwardly through an inclined elongatedtransfer line carbonization zone in contact with a turbulent mass of heated solids of particle size within the range of 50 to 200 mesh, fluidized by an upwardly flowing gas stream having a superficial velocity of about 2 to 30 ft. per second, to form a fluid solids mass of density 0.1 to lbs. per cu. ft. and heated independently of said carbonizable material at least to said carbonization temperature, for a period of from about 0.5 to 15 seconds within said reaction zone sufiicient to carbonize said carbonizable liquids substantially completely to form volatile products and coke, but insufiicient to crack said volatile carbonization products to a substantial degree to gases, controlling the flow velocity of said gas between about 230 it. per second so as to maintain high turbulence of said mass across the cross-sectional area of said path and to force said gas and said mass in the same direction upwardly through said path while preventing substantial back-mixing of solids against the flow direction of the charge, discharging fluidized solids and volatile products from said transfer line reaction zone into a dis engaging zone, withdrawing volatile carbonization products from said zone, passing finely divided coke thus withdrawn, to a combustion zone, subjecting finely divided coke in said combustion zone to a combustion reaction to heat said coke at least to said carbonization temperature, and

passing finely divided coke so heated, from said combustion zone to said transfer line carbonization zone at a rate sufficient to supply at least a portion of the heat of carbonization required in said carbonization zone.

15. The process of producing volatile products from liquid carbonizable fuels of relatively high specific gravity and high viscosity, which comprises passing said fuels at a carbonization temperature of about 850-l400 F. through an elongated narrow path in contact with ,a mass of finely divided solids fluidized by an upwardly flowing gas and heated independently of said cabonizable fuel at least to said carbonization temperature, for a time of about 05-15 seconds sufficient to carbonize said fuels substantially completely but insufficient to permit substantial cracking of volatile carbonization products to gases, controlling the flow velocity of said gas between about 10-30 ft. per second so as to maintain high turbulence of said mass across the cross-sectional area of said path and to force said gas and said mass in the same direction upwardly through said path while preventing substantial back-mixing of solids against the fiow direction of the charge, discharging fluidized solids and volatile products into a disengaging zone, withdrawing finely divided coke from said disengaging zone and withdrawing volatile carbonization products from said disengaging zone.

16. The process of claim 15 in which said disengaging zone is a gas-solids separation zone wherein solids are separated from gas by centrifugal action, and in which said fluidized solids and volatile products are passed directly from said path into said separation zone.

WALTER A. REX.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,858,834 Lucke May 17, 1932 1,941,809 McKee Jan. 2, 1934 1,950,558 Karrick Mar, 13, 1934 2,285,276 Hemminger June 2, 1942 2,301,322 Reeves et a1. Nov. 10, 1942 2,339,932 Kuhl Jan. 25, 1944 2,344,900 Reeves Mar. 21, 1944 2,360,787 Murphree Oct. 17, 1944 2,362,270 Hemminger Nov. 7, 19944 2,412,667 Arveson Dec, 17, 1946 2,412,879 Fischer Dec. 17, 1946' 2,414,586 Eglofi Jan. 21, 1947 2,436,160 Blanding Feb. 17, 1948 2,439,811 Jewell Apr. 20, 1948 

1. TH PROCESS OF PRODUCING VOLATILE FUELS FROM CARBONIZABLE MATERIALS AT A CARBONIZATION TEMPERATURE WHICH COMPRISES PASSING CARBONIZABLE MATERIAL THROUGH AN ELONGATED NARROW PATH IN CONTACTL WITH A MASS OF FINELY DIVIDED SOLIDS FLUIDIZED BY AN UPWARDLY FLOWING GAS AND HEATED INDEPENDENTLY OF SAID CARBONIZABLE MATERIAL AT LEAST TO SAID CARBONIZATION TEMPERATURE, FOR A TIME OF ABUT 0.5-15 SECONDS SUFFICIENT TO CARBONIZE SAID CARBONIZABLE MATERIAL SUBSTANTIALLY COMPLETELY BUT INSUFFICIENT TO PERMIT SUBSTANTIAL CRACKING OF VOLATILE CARBONIZATION PRODUCTS TO GASES, CONTROLLING THE FLOW VELOCITY OF SAID GAS BETWEEN ABOUT 2-30 FT. PER SECOND SO AS TO MAINTAIN HIGH TURBULENCE OF SAID MASS ACROSS THE CROSS-SECTIONAL AREA OF SAID PATH AND TO FORCE SAID GAS AND SAID MASS IN THE SAME DIRECTION UPWARDLY THROUGH SAID PATH WHILE PREVENTING SUBSTANTIAL BACK-MIXING OF SOLIDS AGAINST THE FLOW DIRECTION OF THE CHARGE, DISCHARGING FLUIDIZED SOLIDS AND VOLATILE PRODUCTS INTO A DISENGAGING ZONE, WITHDRAWING FINELY DI- 